Suspension insulator having a cap with internal load transmitting surfaces



May 13, 1969 T. o. VAN TUYL SUSPENSION INSULATOR HAVING A CAP WITH INTERNAL LOAD TRANSMITTING SURFACES Sheet Filed March 16, 1967 2;! [III/1% m T N 2 M m I (I, w 0 w y W 7 BY y M E ATTO-RNEYS May 13, 1969 T. o. VAN TUYL 3,444,314

SUSPENSION INSULA'IOR HAVING A CAP WITH"IN'IERNAL LOAD TRANSMITTING SURFACES Z Filed March 16, 1967 Sheet of 2 INVENTOR 7904 1/45 aux/5,? MW 743%.

EM Me ATTORNEYS United States Patent US. Cl. 174182 8 Claims ABSTRACT OF THE DISCLOSURE An electrical suspension insulator which has a cap and pin formed of aluminum. The cap and pin are electrically separated by a porcelain insulator member. The cap has a pair of axially spaced inclined steps or surfaces at its lower and inner end for aiding in supporting the load applied thereto through the body of the porcelain insulator member which is cemented to the inner surface of the cap. The pair of inclined surfaces are located so as to resist outward spreading action of the terminal edge portion of the cap when vertical loads are applied to the pin of the insulator.

Background of the invention The present invention relates to suspension type electrical insulators wherein a metallic cap is fitted over and is cemented to the upper surface of a porcelain surface or shell. Suspended from the under surface of the porcelain insulator is a pin or stud. The cap has a suitable means, such as a clevis joint, a ball socket, or the like, for connection to a supporting structure, and very substantial vertical loads are applied to the pin and must be supported by the cap and porcelain shell.

In the past, it has been conventional to make the cap and pin of galvanized steel so as to minimize the rust problem and to provide a suspension insulator having sufficient strength to withstand the applied loads. When making the suspension insulator, it has been the usual practice to cement the cap to the porcelain shell and to provide a radially inwardly inclined flange or lip at the terminal periphery of the cap for accommodating a sub stantial portion of the vertical load transmitted to the cap through the shell and bonding concrete.

The prior insulators of the foregoing character have not produced optimum results because of problems that have arisen in connection with rust, weight, cost, and the like. Eiforts have been made to use less corrosive and lightweight materials such as aluminum for the cap and pin, but without complete success. When efforts have been made to use aluminum for this purpose, the cap has been constructed similar to the shape of the known galvanized steel caps. One of the main obstacles to using aluminum for the cap has been its inability to meet high load requirements. It has been found that when relatively heavy vertical loads have been applied to the known aluminum caps, the inclined flanges or lips at the lower terminal edges of the caps have yielded and flared radially outwardly, and the concrete bond has broken away from the caps, resulting in the insulators breaking into two parts.

Summary of invention The presentinvention has overcome the problems relating to meeting the load requirements of the industry, which problems were inherent in aluminum caps heretofore developed for use with suspension insulators, so that now such desirable features as the lightweight and rust resistant properties of aluminum are available in suspension insulators. This has been accomplished by a unique and unobvious change in the construction of the rim or ice lip structure of the cap so that when loads are applied to the cap through the bonding concrete, the lip structure of the cap can withstand greater loads without flaring radial 1y outwardly in the manner of the prior art structures.

Accordingly to one form of the present invention, the cap of the insulator has been formed so that its lip structure or terminal edge portion has an enlarged cross section and a pair of axially spaced steps or inclined surfaces define the radially inner surface of the terminal edge portion. These pair of surfaces are spaced and dimensioned so that the resultant forces acting on the surfaces by the concrete by virtue of axial loads applied to the pin of the insulator, are directed on opposite sides of the center of gravity of the enlarged cross section of the terminal edge portion. Thus, rather than having a single resultant force acting on the lower extremity of the terminal edge portion tending to flare the lower edge radially outwardly, as occurred in the prior art structures, a second surface is provided in the present invention which aids in supporting theinsulator and which results in a second force acting on the terminal flange portion in such a way as to produce a couple tending to turn the terminal flange portion in the opposite direction from that of the first mentioned force, whereby the forces acting to turn the lip or terminal edge portion about its center of gravity act in opposite directions around such center and tend to offset one another. Thus, substantially greater vertical loads can now be carried by the cap without failures of the type which have occurred in prior art caps heretofore formed from aluminum.

Accordingly, it is an object of the present invention to provide an improved suspension insulator which is characterized by its rust resistant properties, it light weight, and its ability to support relatively high vertical loads.

It is another object of the present invention to provide an improved cap for use in suspension insulators of the foregoing character.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

FIGURE 1 is a front elevational view of one form of a suspension insulator embodying the present invention, with portions of the drawing in section to illustrate the terminal lip or edge portion of the cap;

FIGURE 2 is a fragmentary sectional view taken on the line 22 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary section illustrating the encircled portion of FIGURE 1;

FIGURE 4 is an enlarged elevation of a modified form of the cap adapted for use with an insulator of the type shown in FIGURE 1; and

FIGURE 5 is a section taken on the line 5-5 of FIG- URE 4.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangemen of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring now to the drawings, the invention will be described in greater detail. The suspension insulator 10 has a conventional pin 12 which is cemented, as shown at 14, to a conventional porcelain shell or insulating element 16. The ball-socket type cap 18 is cemented to the upper surface of the shell 16, as shown at 20. The cap 18 has a conventional ball-socket joint 22 for supporting the suspension insulator 10 from a ball fitting (not shown) connected to a supporting structure.

As previously indicated, very substantial vertical loads may be imparted in use to the pin 12 which then must be transmitted through the shell 16 to the cap 18 and its ball-socket joint 22. These loads are transmitted from the pin 12 through the cement material 14 to the shell 16, and from the shell 16 through the cement material 20 to the cap 18.

Referring now to FIGURE 3, which is an enlarged detail in section of the encircled portion of FIGURE 1, a brief description will be given of the terminal edge or lip portion or structure 24, and the manner in which the vertical loads applied to pin 12 are believed to be accommodated by the terminal edge or lip portion 24 so as to enable the cap 18 to carry such loads without having its lower lip flare radially outwardly, as has occurred with prior art structures.

For the purpose of description, the terminal edge portion 24 is considered to be that portion of the cap located below the broken reference line 26, appearing in FIG- URE 3. As there shown, the terminal edge portion 24 is enlarged beyond the normal wall thickness of the cap 18 and has its radially inner surface defined by a pair of axially spaced steps having conic or inclined surfaces 28 and 30. Preferably, the surfaces 28 and 30 are parallel to one another, and are inclined relative to the axis of the cap 18 at an angle of 22 /2. The surfaces 28 and 30 are also dimensioned and spaced so that the resultant components of force acting on each of these surfaces as a result of a load applied to pin 12 will be directed on opposite sides of the center of gravity of the cross section of the terminal edge portion. Thus, the broken line 32 is an extension of the resultant force F which acts on the surface 28, and the broken line 34 is an extension of the resultant force F which acts on the surface 30. The resultant forces F and F represent the components of tforce acting against the surfaces 28 and 30 as a result of loads applied to pin 12. The center of gravity of the cross section of terminal edge pontion is approximately at the point 36, so that the force F attempts to turn the terminal edge portion 42 in a clockwise direction around the center of gravity 36 and the force F attempts to turn the terminal edge portion 24 in a counterclockwise direction around the center of gravity 36. Thus, these forces tend to offset one another, so that the cap 18 does not flare out or spread apart at its lower extremity when a load is applied to the pin as do prior art caps which have been made of aluminum, but according to prior designs for steel caps. The unique and unobvious solution to the problem relating to load carrying capacity of aluminum caps in suspension insulators has in this manner been solved so that the cap 18 can be formed easily and economically by a casting operation and in use can carry surprisingly heavy loads. The cap 18 is then readily joined to the other components in conventional operations to form the new and improved suspension insulator 10.

The present invention is not limited to the specific sup porting means 22 for the cap 18. As shown in FIGURES 4 and a cap 118 may have a clevis type support 122 in place of the ball-socket means 22. However, this form of the invention also has a terminal edge portion 124 which conforms to the teachings of the present invention.

Having thus described my invention, I claim:

1. A suspension insulator having a cap, a porcelain shell cemented to the interior of said cap and a pin cemented to the interior of said shell, wherein the improvement comprises said cap having an enlarged cross section throughout its terminal edge portion, and a pair of axially spaced steps defining the radially inner surface of said terminal edge portion, said steps including conic surfaces in parallel relationship inclined radially inwardly from the axially inner to the axially outer end of said cap, and the terminal edge portion having a center of gravity therein located within a zone radially outward from and between the inner and outer ends of the conic surface nearest the axially outer end of the cap and between resultant force lines extending normal to each conic surface from locations midway between the axially inner and outer ends of such surfaces.

2. A suspension insulator according to claim 1, wherein the angle of inclination of each of said conic surfaces to the vertical is about 22 /2 3. A suspension insulator according to claim 1, wherein the cap has a clevis-type fitting on its upper surface.

4. A suspension insulator according to claim 1, wherein the cap has a ball-socket type fitting on its upper surface.

5. A suspension insulator according to claim 1, wherein the cap is formed of aluminum.

6. An article of manufacture for use in a suspension insulator comprising a metallic casting defining a cap for said insulator, said cap having attachment means at its apex for connecting the cap to a supporting structure and a terminal lip structure for supporting the remainder of the insulator, said terminal lip structure having a larger cross section than the remaining wall structure of the cap and a pair of axially spaced inwardly and downwardly inclined stepped conic surfaces defining the radially inner surface of said terminal lip structure, said terminal lip structure having a center of gravity therein located within a zone radially outward from and between the inner and outer ends of the conic surface nearest the axially outer end of the cap and between resultant force lines extending normal to each conic surface from locations midway between their axially inner and outer ends.

7. An article of manufacture according to claim 6, wherein the metallic material of said casting is aluminum.

8. An article of manufacture according to claim 6, wherein said inclined surfaces are parallel and are inclined at about 22 to the axis of the cap.

References Cited UNITED STATES PATENTS 1,684,441 9/1928 Gouverneur 174-182 1,822,485 9/1931 Hawley 174-182 1,937,620 12/1933 Austin 174-182 2,008,414 7/1935 Fischer 174-182 3,011,014 11/1961 Pentecost 174-186 X 3,217,095 11/1965 Ross et al 174-186 X LARAMIE E. ASKIN, Primary Examiner.

US. Cl. X.R. 

